1. Technical Field
The present invention relates to a control device and a control system usable for identifying control devices in a control system including a plurality of control devices connected with each other via such as a wire harness.
2. Background Art
In a vehicle, various loads such as a lamp, an electric motor, and a heater, and input elements such as a switch and a sensor are separately disposed at various places of the vehicle body as electrical components. Therefore, in a case of designing an onboard system with the plurality of loads and input elements, it is possible to reduce length, weight and power loss of a wire harness by arranging each of electronic control units (ECU) at position close to corresponding electric component.
However, in order to control all the electrical components in the vehicle in cooperation with each other, it is necessary to connect the plurality of electronic control units with each other via a communication line, so as to exchange instructions or data therebetween. A plurality of slave control units and at least one master control unit may be used. In this case, the master control unit manages the plurality of slave control units.
As mentioned above, in a control system in which a plurality of electronic control units are connected with each other via a common communication line, it is necessary to identify a connection source node and a destination node of each of the electronic control units during data communication thereof by using a unique identifier (ID). However, in an actual system in a vehicle, it is a must to consider how to assign identifiers to the electronic control units at nodes since the number of electronic control units and the number and types of connected electrical components may change variously.
For example, in an onboard machine control system in JP-A-2010-195133, a resistor is incorporated in each slave device. A slave device is configured to detect a DC voltage at a terminal of a resistor, so as to specify an identifier.
Also, in a control system in JP-A-2012-1180, an electronic control device (ECU) is configured to be capable of assigning node ID to a vehicle component connected thereto. Specifically, the control system includes an injector for each cylinder incorporating a press sensor and a communication driver, and the ECU bus-connected to the communication driver of the injector via a common communication line, such that a sensor signal from the press sensor is input into the ECU via a sensor line of the injector. After outputting a prescribed instruction for assigning node ID to the injector to the communication line, the ECU performs a process in which the sensor line of the injector is set to a ground voltage only at a time corresponding to the assigning node ID. Upon receiving the instruction, the injector measures time when the sensor line thereof is at the ground voltage, and specifies node ID based on the time.
Also, in a master-slave system in JP-A-2014-230097, there is disclosed a technique for determining node ID of a slave device easily, and for adding a slave device or detecting a breakdown easily at the same time.
Specifically, the master-slave system is configured to common bus-connect a master device and each slave device separately via a serial signal line and to connect the master device and each slave device separately via a daisy chain, and that a response message of a slave device in communication contains flag information containing a node ID setting state of another device and indicating a state of an upper stage device and a connection state of a lower stage device.
However, in a case as JP-A-2010-195133, where a particular component such as a resistor corresponding to an assigned identifier is incorporated into a slave device individually, an increase in component costs and manufacturing costs of slave devices is inevitable since types and part numbers of the slave devices are different with each other.
Also, in a case as JP-A-2012-1180, where an electronic control device assigns node ID to subordinate vehicle components, the electronic control device cannot identify a plurality of vehicle components in an initial state before assigning correct node ID. Therefore, there will be a problem, for example, signals transmitted by the plurality of vehicle components collide on the common communication line, and that time required until the entire system achieves a correctly operating state is inevitably long.
Even in a case as JP-A-2014-230097, where a response message of a slave device contains flag information containing a node ID setting state of another device and indicating a state of an upper stage device and a connection state of a lower stage device, the entire system cannot achieve a correctly operating state without a complicated time consuming communication procedure since node ID of slave devices is not determined in the initial state.
In a case as JP-A-2012-1180 and JP-A-2014-230097, where a higher-order control device determines node ID of lower-order control devices, there is a problem that the higher-order control device cannot grasp types of electrical components connected to output sides of the lower-order control devices. Therefore, in a circumstance as an onboard system, where various types of electrical components are connected to outputs of lower-order control devices, the lower-order control devices have to perform their own controls separately. As a result, an increase in component costs and manufacturing costs is inevitable since configurations and operation of the lower-order control devices cannot be commonized. Also, in a case of, for example, adding another electrical component to the system, significant changes have to be made to the operation of the control devices, and an increase in development costs is expected.
Considering the above matters, the present inventor devised the prior art prior to the present invention, through which a combination of potentials of a plurality of input ports in control devices in a steady state is associated with ID. According to the prior art, configurations of the control units can be commonized, and ID can be specified via, for example, a difference between connection states of the wire harness connected to the control devices.
However, in a case of adopting the above prior art, it is necessary to take a long time to some degree to determine that the control devices are in a steady state when specifying ID. This is because that, if a sufficient time is not cost, there is a concern that a wrong signal potential will be read, and that wrong ID will be assigned under an influence of such as chattering of a switch contact.
However, in the case of adopting the above prior art, a delay happens to operation of the entire system since it costs time for the control devices to specify their own ID. For example, waiting time until when electrical components in a vehicle achieve a normal operating state is long at start of an engine of the vehicle.
For example, if constant data of ID is kept in such as a ROM (read only memory) in advance, the above waiting time can be eliminated since it is unnecessary to monitor a signal that may change. However, it is not possible to add or reattach another electrical component in a factory or at a dealer's, since ID cannot be made flexible in that case. Also, in a case where a mistake is made in writing data corresponding to a component such as a ROM in such as a factory, this component becomes unusable and has to be disposed of.
Meanwhile, in the case of adopting the above prior art, a contact failure resulting from such as aged deterioration may happen in a place connected with the input ports. In this way, ID assigned to control units may change freely, causing malfunction of the electrical components.
The present invention is made in view of the above circumstances, and an object thereof is to provide a control device and a control system capable of commonizing configurations and operation of a plurality of control devices included in a system, and shortening waiting time required for specifying ID and changing ID assigning as necessary at the same time.